HHB 1.2 Diagnostic Questions

Select the true statements about the structure of DNA

• it has a double helix shape

• the two strands are parallel

• it contains amino acids

• It is made of repeated units called bases

• one strand starts with a phosphate & other with a deoxyribose sugar

Answer explanation

has to be double STRANDED helix

strands are ANTI-parallel

DNA is made of NUCLEOTIDES, a base is only one component of these repeating units

the DNA base sequence contains the code for the amino acid sequence in the protein

select the correct base pairing found in DNA

• Uracil pairs with Adenine

• Uracil pairs with Thymine

• A-T and G-C

• Cytosine with Guanine

• Thymine can bind to Adenine

Answer explanation

DNA doesnt have a Uracil base

Using letters and dashes or just saying with is not acceptable

The role of primers is to

• all genes to be expressed

• switches off certain genes and turns on others

• unwinds and unzips the DNA

• bind to the 3' end of the strand and replicate the DNA

• allow DNA replication to begin

Answer explanation

primers are not involved in gene expression

Although the DNA must unwind and unzip before DNA replication, we dont teach you the name of the enzyme which does this, so you just state it happens

The primers do bind to 3' end of each DNA strand, but suggesting the PRIMER replicates the DNA negates the answer

select all of the accurate statements about the enzyme DNA polymerase

• unwinds and unzips the DNA

• adds and joins nucleotides to the 3' end of new strand

• requires primers to begin

• adds and joins nucleotides to the primer

• adds and joins nucleotides to the 3' end of the strand

select the true statements about ligase

• its joins the fragments of the lagging strand together

• its joins the fragments of the leading strand together

• it replicates the lagging strand

• it joins the new DNA fragments on the lagging strand together

• it glues the DNA fragments on the lagging strand

select the purpose(s) of PCR

• to make copies of a target sequence of DNA

• to amplify DNA sequences

• to help solve crimes as a person's DNA is unique to them

• to settle paternity suits

• to identify diseases and disorders

which statements describes a practical application of PCR

• DNA acts as a fingerprint to help solve crimes

• to identify the mother as part of a paternity suit

• to diagnose an illness or disease

• to identify which type of mutation

• diagnose genetic disorders

Answer explanation

finger prints and DNA are both unique to a person but to say that DNA is a fingerprint is not accurate

the DNA sequence can be used ot diagnose genetic disorders as these incorrect sequences are known and can be targetted with specific primers

However, this is about the person;s DNA sequences, disease, general disorders or illness cant be diagnosed

In PCR the solution is heated to 95 oC so that

• the DNA unwinds and unzips

• primers can bind to the 3' end of the target sequences

• the hydrogen bonds are broken to separate the DNA strands

• to break the peptide bonds between the amino acids

• to break the hydrogen bonds between the amino acids

In PCR the solution is heated to 55 oC so that

• to amplify the DNA

• primers can bind to the 3' end of the target sequences

• the hydrogen bonds are broken to separate the DNA strands

• for heat tolerant DNA polymerase to replicate the target sequence

• for heat tolerant DNA polymerase to replicate the DNA

select all of the chemicals involved in PCR at 75 oC

• Ligase

• Primers

• free DNA nucleotides

• Heat tolerant RNA polymerase

• Heat tolerant DNA polymerase

Answer explanation

there is no lagging and leading strands only single strands so no ligase

at 75oC the target sequence is replciated this needs:

The enzyme to replicate

the nucleotides to build the new strand from

and the primer to allow replication to begin